Extensible Provisioning Protocol (EPP) Transport over HTTPS
draft-ietf-regext-epp-https-04

Internet Engineering Task Force                              M. Loffredo
Internet-Draft                                      L. Luconi Trombacchi
Intended status: Standards Track                           M. Martinelli
Expires: 7 March 2027                                IIT-CNR/Registro.it
                                                             D. Keathley
                                                                J. Gould
                                                          VeriSign, Inc.
                                                        3 September 2026

      Extensible Provisioning Protocol (EPP) Transport over HTTPS
                     draft-ietf-regext-epp-https-04

Abstract

   This document describes how an Extensible Provisioning Protocol (EPP)
   connection is mapped onto the Hypertext Transfer Protocol (HTTP).
   EPP over HTTP (EoH) requires the use of Transport Layer Security
   (TLS) to secure EPP information (i.e. HTTPS).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 7 March 2027.

Copyright Notice

   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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   extracted from this document must include Revised BSD License text as
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Session Management  . . . . . . . . . . . . . . . . . . . . .   4
   4.  Message Exchange  . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Message Exchange Example  . . . . . . . . . . . . . . . .   8
   5.  Transport Considerations  . . . . . . . . . . . . . . . . . .  11
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
     6.1.  EPP Extension Registry  . . . . . . . . . . . . . . . . .  12
   7.  Implementation Status . . . . . . . . . . . . . . . . . . . .  12
     7.1.  Verisign EPP SDK  . . . . . . . . . . . . . . . . . . . .  12
     7.2.  IIT-CNR/Registro.it . . . . . . . . . . . . . . . . . . .  13
   8.  Operational Considerations  . . . . . . . . . . . . . . . . .  13
     8.1.  Operational Impact  . . . . . . . . . . . . . . . . . . .  14
     8.2.  Configuration and Deployment  . . . . . . . . . . . . . .  14
     8.3.  Performance and Scalability . . . . . . . . . . . . . . .  15
     8.4.  Monitoring and Logging  . . . . . . . . . . . . . . . . .  15
     8.5.  Security and Fault Management . . . . . . . . . . . . . .  15
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     11.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Appendix A.  Change History . . . . . . . . . . . . . . . . . . .  19
     A.1.  Change from 02 to 03  . . . . . . . . . . . . . . . . . .  19
     A.2.  Change from 03 to 04  . . . . . . . . . . . . . . . . . .  19
     A.3.  Change from 04 to 05  . . . . . . . . . . . . . . . . . .  19
     A.4.  Change from regext 00 to regext 01  . . . . . . . . . . .  19
     A.5.  Change from regext 01 to regext 02  . . . . . . . . . . .  19
     A.6.  Change from regext 02 to regext 03  . . . . . . . . . . .  19
     A.7.  Change from regext 03 to regext 04  . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

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1.  Introduction

   This document describes how EPP [RFC5730] is mapped onto the
   Hypertext Transfer Protocol (HTTP) [RFC9110].  Note that there are
   several versions of HTTP currently in use, including: HTTP/1.1
   [RFC9112], HTTP/2 [RFC9113], and HTTP/3 [RFC9114].  As the
   differences among such versions do not affect the EPP mapping
   described in this document, hereinafter the version number is omitted
   except for presenting the special features in the underlying layers
   of the HTTP stack.

   HTTP represents a higher-level abstraction of a network connection,
   removing the need to directly deal with all of the lower-level
   details of transport protocols.  This makes HTTP much more compatible
   with cloud-native infrastructures, and facilitates faster development
   times and reduced maintenance costs in such environments.

   This mapping uses POST requests and 200 (OK) responses, effectively
   tunnelling EPP semantics and preserving its connection orientation.
   This promotes reuse of existing EPP software with minimal
   modification, but limits the use of HTTP features the surrounding
   infrastructure otherwise provides -- caching, multiplexing,
   authentication, logging, and automated retries.

   Security services beyond those defined in EPP are provided by TLS via
   HTTPS Section 4.2.2 of [RFC9110].

2.  Terminology

   This document makes use of the following terms:

   EoH:  The acronym used for the EPP over HTTPS transport that defines
      the use of HTTPS as an EPP transport following the considerations
      in Section 2.1 of [RFC5730].

   EPP connection:  Is a client-server connection, defined in
      Section 2.1 of [RFC5730], that supports the EPP Server State
      Machine, defined in Section 2 of [RFC5730].  The EoH connection is
      an EPP connection mapped onto the Hypertext Transfer Protocol
      (HTTP) using an HTTP session.

   EPP session:  Is an authenticated EPP connection, using the Session
      Management Commands defined in Section 2.9.1 of [RFC5730].  The
      EoH session is an EPP session mapped onto the Hypertext Transfer
      Protocol (HTTP) using an HTTP session.

   EoH connection:  Is an EPP client-server connection, defined in

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      Section 2.1 of [RFC5730], that is mapped onto the Hypertext
      Transfer Protocol (HTTP) using an HTTP session.  Upon the client
      submitting the initial HTTP POST with empty content, the HTTP
      session is started by the server and the server returns an EPP
      <greeting>, establishing the EoH connection.

   EoH session:  Is an authenticated EoH connection, which occurs after
      a successful EPP <login> on an EPP connection.  In EPP, all
      messages except for the EPP <login> and <hello> need to be sent on
      an EPP session.

   HTTP session:  Used to facilitate a stateful EoH connection / EoH
      session that is required by Section 2.1 of [RFC5730].  The HTTP
      session is initiated using the Set-Cookie and Cookie header fields
      when the EoH connection is established.  EPP messages belonging to
      the same EoH connection can be exchanged over different underlying
      HTTP connections.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Session Management

   Mapping EPP session management facilities onto HTTP is accomplished
   using the existing HTTP POST method.  An EPP session exists on top of
   an EPP connection between two peers, one that initiates the
   connection request and one that responds to the connection request.
   The initiating peer is called the "client", and the responding peer
   is called the "server".  An EPP server implementing this
   specification MUST listen for HTTPS requests at the server URL made
   available to clients.  When the URL does not specify a port, the
   default HTTPS port 443 is used.  There is no server discovery
   mechanism defined for EoH.  The server URL for EoH is made available
   out-of-band by the server to the clients.

   Even though HTTP itself is stateless, a stateful EPP session can be
   achieved using the mechanism described in [RFC6265].  This mechanism
   uses the Set-Cookie and Cookie header fields to facilitate a stateful
   HTTP session.  Such a session is initiated by the client by sending
   an initial POST request with empty content to the server.  The POST
   request MUST include "application/epp+xml" (Appendix B of [RFC5730])
   in the Accept header field.  Upon successful establishment of an EoH
   connection, the server MUST return a 200 (OK) HTTP response
   containing the EPP Greeting.  The response MUST include "application/
   epp+xml" in the Content-Type header field, together with the

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   character encoding of the EPP XML (e.g., "application/
   epp+xml;charset=UTF-8"), and a Cache-Control header field containing
   the "no-store" directive to disable caching.  The response MUST also
   include the X-Content-Type-Options header field with the value
   "nosniff" to stop clients from guessing a file's format.  The server
   MUST use the Set-Cookie header field to include a token that uniquely
   identifies the HTTP session.  The client MUST include that cookie in
   all subsequent requests belonging to the EoH connection, and the
   server MUST treat those requests as part of the same EoH connection.
   If a 200 (OK) response does not include a Content-Type header field
   indicating "application/epp+xml", the client MUST treat the response
   as invalid and fail the EoH connection process.  If the client
   receives a final HTTP status code other than 200 in response to the
   initial POST request, no EoH connection has been established and the
   client MUST treat the response as a failure of the connection
   process.  The handling of such a response is governed by the HTTP
   status-code semantics described in Section 4.  The HTTP session
   represents an EPP connection, referred to as an EPP over HTTP (EoH)
   connection, which is initiated by the initial POST request with empty
   content.

   The EPP session begins with a successful EPP <login> command on the
   EoH connection and can be referred to as an EPP over HTTP (EoH)
   session.

   An EPP session is normally ended by the client issuing an EPP
   <logout> command.  A server receiving an EPP <logout> command MUST
   end the EPP session.  A server MAY also end an EPP session that has
   been either active or inactive for longer than a server-defined
   period.  A server MAY end the HTTP session after ending the EPP
   session.

4.  Message Exchange

   EPP describes client-server interaction as a command-response
   exchange where the client sends one command to the server and the
   server returns one response to the client.  With the exception of the
   EPP Greeting, EPP messages are initiated by the EPP client in the
   form of EPP commands.  An EPP client MUST send all commands as HTTP
   POST requests (Section 6.4 of [RFC9110]).  Each POST request MUST
   include the HTTP session identifier in the Cookie header field and
   "application/epp+xml" in the Accept header field.  When an HTTP
   request carrying an EPP command reaches the EPP processing layer, the
   EoH server MUST return the corresponding EPP response in the HTTP
   response.  The HTTP request carrying the EPP command and the HTTP
   response carrying the EPP response MUST include "application/epp+xml"
   in the Content-Type header field, together with the character
   encoding of the EPP XML (e.g., "application/epp+xml;charset=UTF-8").

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   The EPP response MUST include "no-store" in the Cache-Control header
   field to disable caching.

   HTTP does not define the POST method as idempotent.  This does not
   prevent an application from assigning idempotent semantics to the
   content of a particular POST request.  As specified in Section 2 of
   [RFC5730], EPP commands are designed so that they can be made
   idempotent.  An EoH client that does not receive a valid EPP response
   MAY retry the HTTP POST request only when the failure might be
   transient, retrying is consistent with the semantics of any HTTP
   status code received, and the client knows that the enclosed EPP
   command, including any extensions, has idempotent application
   semantics, as permitted by Section 9.2.2 of [RFC9110].  The retry
   MUST contain the same EPP command, including the same client
   transaction identifier, if present.  The client MUST NOT send a
   subsequent EPP command until it has received a valid response to the
   command being retried or has abandoned the EPP session.  Operators
   MUST configure HTTP intermediaries under their control not to
   automatically retry an EPP POST request.  Automatic retry behavior is
   limited to EoH clients that understand the idempotent semantics of
   EPP commands and preserve their ordering.

   The EPP command XML is framed by the content of the HTTP POST
   request, and the EPP response XML is framed by the content of the
   HTTP response.  Except for the initial POST request described in
   Section 3, each EoH HTTP request MUST contain a single EPP message.
   Each HTTP response generated after processing an EPP command MUST
   contain a single EPP response.  Commands MUST be processed
   independently and in the same order as received from the client.

   HTTP status codes MUST NOT be used to convey the result of an EPP
   command.  When an EoH server accepts an HTTP request for EPP
   processing and generates an EPP response, it MUST return that
   response with the HTTP status code 200 (OK), regardless of whether
   the EPP response indicates command success or failure.  This
   requirement applies only to responses generated after the request has
   reached the EPP processing layer.  If an HTTP request cannot be
   delivered to or accepted for EPP processing, the EoH server or an
   HTTP intermediary can return any status code applicable under HTTP.
   Examples include malformed HTTP requests, unsupported media types,
   request-size limits, rate limits, overload conditions, and gateway
   failures.  Such a response represents an HTTP-layer outcome and is
   not an EPP response.  EoH clients MUST be prepared to receive any
   HTTP status code.  Clients MUST process unrecognized status codes
   according to the status-code class semantics defined in Section 15 of
   [RFC9110].  If a client does not receive a valid EPP response, it has
   not received an authoritative EPP command result.  The client MUST
   process any HTTP response according to its status-code semantics.  If

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   the request might have reached the EPP processing layer but no valid
   EPP response is received, the outcome of the EPP command is
   indeterminate.

   If a request containing an EPP command and either an empty or an
   invalid HTTP session identifier reaches the EPP processing layer, the
   server MUST return an EPP 2002 response (i.e. Command use error) in a
   200 (OK) HTTP response.

   A server SHOULD impose a limit on the amount of time required for a
   client to issue a well-formed EPP command.  A server SHOULD end an
   EPP session if a well-formed command is not received within the time
   limit.

   HTTP/2 and HTTP/3 support a multiplexing feature that was introduced
   to address head-of-line blocking issues in previous HTTP versions.
   In the context of multiple requests being sent on a single HTTP
   connection, multiplexing allows the delivery of responses in a
   different order from how the requests were made.  EPP allows
   pipelining of commands, but this mapping does not enable it.  While
   HTTP is capable of having more than one outstanding request (through
   pipelining or multiple connections in HTTP/1, and multiplexing in
   later versions), this mapping explicitly forbids it.  Clients MUST
   NOT have more than one outstanding HTTP request per EPP session at
   any given time.  Regardless of the client not using EPP pipelining,
   an intermediary can produce concurrent HTTP requests per EPP session,
   so the server MUST define the behavior when EPP pipelining is
   identified (i.e. fail or serialize HTTP requests).

   A general state machine for an EPP server is described in Section 2
   of [RFC5730].  A general client-server message exchange using HTTP is
   illustrated in Figure 1.

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        Client                  Server
   |                   |
   |  POST <empty content> Server URL    |
   | >>------------------------------->> |
   |                   |
   |             Send Greeting           |
   | <<-------------------------------<< |
   |                   |
   |             POST <login>            |
   | >>------------------------------->> |
   |                   |
   |             Send Response           |
   | <<-------------------------------<< |
   |                   |
   |            POST Command X           |
   | >>------------------------------->> |
   |                   |
   |            Send Response X          |
   | <<-------------------------------<< |
   |                   |
   |            POST Command Y           |
   | >>------------------------------->> |
   |                   |
   |            Send Response Y          |
   | <<-------------------------------<< |
   |                  .|
                                        .
                                        .
   |            POST <logout>            |
   | >>------------------------------->> |
   |                   |
   |            Send Response            |
   | <<-------------------------------<< |

               Figure 1: HTTP Client-Server Message Exchange

   The EPP server MUST follow the "EPP Server State Machine" procedure
   described in [RFC5730].

4.1.  Message Exchange Example

   This section includes an example message exchange used to establish
   the EoH session, which includes the initial EoH connection that
   returns the EPP <greeting>, followed by the EPP <login> command and
   EPP response.  The example EPP XML is taken from [RFC5730].

   Example of the initial EoH connection using an HTTP POST with empty
   content to establish the EoH connection:

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   POST / HTTP/1.1
   Host: eoh.example.com
   Accept: application/epp+xml

                 Figure 2: Example Initial EoH Connnection

   Example of the initial EoH connection response containing the HTTP
   session identifier and the EPP <greeting> content that establishes
   the EoH connection:

   HTTP/1.1 200 OK
   Cache-Control: no-store
   Content-Type: application/epp+xml;charset=UTF-8
   Content-Length: 815
   Set-Cookie: session_id=xyz1234567; Secure; HttpOnly; SameSite=Strict

   <?xml version="1.0" encoding="UTF-8" standalone="no"?>
   <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
     <greeting>
       <svID>Example EPP server epp.example.com</svID>
       <svDate>2000-06-08T22:00:00.0Z</svDate>
       <svcMenu>
         <version>1.0</version>
         <lang>en</lang>
         <lang>fr</lang>
         <objURI>urn:ietf:params:xml:ns:obj1</objURI>
         <objURI>urn:ietf:params:xml:ns:obj2</objURI>
         <objURI>urn:ietf:params:xml:ns:obj3</objURI>
         <svcExtension>
           <extURI>http://custom/obj1ext-1.0</extURI>
         </svcExtension>
       </svcMenu>
       <dcp>
         <access><all/></access>
         <statement>
           <purpose><admin/><prov/></purpose>
           <recipient><ours/><public/></recipient>
           <retention><stated/></retention>
         </statement>
       </dcp>
     </greeting>
   </epp>

             Figure 3: Example Initial EoH Connnection Response

   Example sending of the EPP <login> command to authenticate the client
   and establish the EoH session.:

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   POST / HTTP/1.1
   Host: eoh.example.com
   Accept: application/epp+xml
   Content-Type: application/epp+xml;charset=UTF-8
   Content-Length: 664
   Cookie: session_id=xyz1234567

   <?xml version="1.0" encoding="UTF-8" standalone="no"?>
   <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
     <command>
       <login>
         <clID>ClientX</clID>
         <pw>foo-BAR2</pw>
         <newPW>bar-FOO2</newPW>
         <options>
           <version>1.0</version>
           <lang>en</lang>
         </options>
         <svcs>
           <objURI>urn:ietf:params:xml:ns:obj1</objURI>
           <objURI>urn:ietf:params:xml:ns:obj2</objURI>
           <objURI>urn:ietf:params:xml:ns:obj3</objURI>
           <svcExtension>
             <extURI>http://custom/obj1ext-1.0</extURI>
           </svcExtension>
         </svcs>
       </login>
       <clTRID>ABC-12345</clTRID>
     </command>
   </epp>

                   Figure 4: Example EPP <login> Command

   Example EPP <login> response that establishes the EoH session:

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   HTTP/1.1 200 OK
   Cache-Control: no-store
   Content-Type: application/epp+xml;charset=UTF-8
   Content-Length: 320

   <?xml version="1.0" encoding="UTF-8" standalone="no"?>
   <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
     <response>
       <result code="1000">
         <msg>Command completed successfully</msg>
       </result>
       <trID>
         <clTRID>ABC-12345</clTRID>
         <svTRID>54321-XYZ</svTRID>
       </trID>
     </response>
   </epp>

                   Figure 5: Example EPP <login> Response

5.  Transport Considerations

   Section 2.1 of [RFC5730] describes considerations to be addressed by
   protocol transport mappings.  This document addresses each of those
   considerations using a combination of features of the HTTP protocol
   itself and features of this document.

   *  Command Order: Section 4 includes a requirement for ordered
      message delivery.

   *  Session Mapping: EPP session management is described in Section 3
      of this document.

   *  Stateful Nature: Achieving the stateful nature of EPP is described
      in Section 3.

   *  Frame Data Units: Section 4 of this document describes how each
      EPP command is framed within the content of HTTP requests and
      responses.

   *  Congestion Avoidance: Section 3.9.3 of [RFC8095] confirms
      congestion avoidance as a feature of HTTP.

   *  Reliability: Section 3.9.3 of [RFC8095] confirms reliable message
      delivery as a feature of HTTP.

   *  Pipelining: Section 4 of this document stipulates that command
      pipelining must not be used in EoH.

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6.  IANA Considerations

6.1.  EPP Extension Registry

   The EPP transport described in this document should be registered by
   IANA in the "Extensions for the Extensible Provisioning Protocol
   (EPP)" registry described in RFC 7451 [RFC7451].  The details of the
   registration are as follows:

   Name of Extension:  "Extensible Provisioning Protocol (EPP) Transport
      over HTTPS"
   Document status:  Standards Track
   Reference:  (This specification)
   Registrant Name and Email Address:  IESG, <iesg@ietf.org>
   Top-Level Domains(TLDs):  Any
   IPR Disclosure:  None
   Status:  Active
   Notes:  None

7.  Implementation Status

   Note to RFC Editor: Please remove this section and the reference to
   [RFC7942] before publication.

   This section records the status of known implementations of the
   protocol defined by this specification at the time of posting of this
   Internet-Draft, and is based on a proposal described in [RFC7942].
   The description of implementations in this section is intended to
   assist the IETF in its decision processes in progressing drafts to
   RFCs.  Please note that the listing of any individual implementation
   here does not imply endorsement by the IETF.  Furthermore, no effort
   has been spent to verify the information presented here that was
   supplied by IETF contributors.  This is not intended as, and must not
   be construed to be, a catalog of available implementations or their
   features.  Readers are advised to note that other implementations may
   exist.

   According to [RFC7942], "this will allow reviewers and working groups
   to assign due consideration to documents that have the benefit of
   running code, which may serve as evidence of valuable experimentation
   and feedback that have made the implemented protocols more mature.
   It is up to the individual working groups to use this information as
   they see fit".

7.1.  Verisign EPP SDK

   Organization: Verisign Inc.

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   Name: Verisign EPP SDK

   Description: The Verisign EPP SDK includes both a full client
   implementation and a full server stub implementation of this
   specification.  Both HTTP/1.1 and HTTP/2 were implemented, but HTTP/3
   was not due to the lack of support of the underlying library.

   Level of maturity: Development

   Coverage: All aspects of the protocol are implemented with HTTP/1.1
   and HTTP/2.

   Licensing: GNU Lesser General Public License

   Contact: jgould@verisign.com

   URL: https://www.verisign.com/en_US/channel-resources/domain-
   registry-products/epp-sdks

7.2.  IIT-CNR/Registro.it

   Organization: Institute of Informatics and Telematics of National
   Research Council (IIT-CNR)/Registro.it

   Name: .it EPP client and server

   Description: This specification has been partially implemented on
   both the client and server sides.  A slightly different
   implementation, which initiates the HTTP session upon completion of
   an EPP Login request, has been running on the live platform since
   2009.  Registro .it is currently working to release a fully compliant
   implementation to the public test environment.

   Level of Maturity: This is an implementation running in the live
   platform.

   Coverage: This implementation includes all the functionality
   described in this specification, except that the HTTP session begins
   after an EPP Login request has been successfully processed.

   Contact Information: Mario Loffredo, mario.loffredo@iit.cnr.it

8.  Operational Considerations

   This section addresses the operational aspects of transporting EPP
   over HTTPS, as outlined in [I-D.ietf-opsawg-rfc5706bis].

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8.1.  Operational Impact

   Infrastructure Reuse:  Moving from EPP over TCP to EPP over HTTPS
      simply involves replacing the transport management layer on top of
      the existing implementation.  Therefore, operators who already
      provide EPP over TCP can reuse much of their infrastructure.
      Additionally, they can leverage standard web infrastructure such
      as HTTP load balancers, firewalls, and Web Application Firewalls
      (WAF) to enable HTTPS connections of EPP sessions.

   EPP Connection Management:  EPP is a stateful protocol, and the EPP
      connection state defined in [RFC5730] needs to be preserved across
      the HTTP request-response exchanges that form an EoH connection.
      As described in Section 3, an EoH connection is identified by an
      HTTP session identifier and represents an EPP connection.  In a
      deployment consisting of multiple EoH server instances, operators
      can maintain this state using either session affinity or a shared
      session store.  With session affinity ("sticky sessions"), the
      state is maintained locally by an EoH server instance, and the
      load balancer routes all HTTP requests containing the same session
      identifier to that instance.  If the selected instance becomes
      unavailable, the associated EoH connections are lost unless their
      state is replicated or another recovery mechanism is provided.
      Alternatively, operators can maintain the connection state in an
      external shared session store.  This allows any EoH server
      instance to process a request belonging to an existing EoH
      connection and avoids dependence on a particular backend instance.
      It can therefore facilitate backend maintenance, failover, and
      horizontal scaling without terminating active EoH connections.  A
      shared session store is part of the availability and security
      boundary of the EoH service.  Operators using this approach MUST
      protect the confidentiality and integrity of the stored state and
      SHOULD avoid making the store a single point of failure.  They
      MUST also ensure that requests belonging to the same EoH
      connection are processed sequentially and that changes to its
      state are applied atomically.  The lifetime of the stored
      connection state MUST be coordinated with the lifetimes of the
      corresponding HTTP and EPP sessions to prevent stale connection
      state or premature session termination.

8.2.  Configuration and Deployment

   Port Management:  While EPP over TCP uses port 700 by default, EPP
      over HTTPS uses the default HTTPS port 443.  This facilitates
      easier traversal of corporate firewalls but requires careful
      separation of EPP traffic from regular web traffic on the same
      infrastructure (e.g., via specific subdomains or URL paths).

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   TLS Configuration:  Consistently with [RFC9325], operators MUST
      maintain up-to-date TLS configurations.  Operational procedures
      SHOULD include regular audits of supported cipher suites and
      certificate renewal processes to prevent service outages.

8.3.  Performance and Scalability

   Overhead:  HTTPS introduces additional overhead compared to raw TCP
      due to HTTP header fields and the TLS handshake.  However, the use
      of HTTP/2 or HTTP/3 can mitigate some of this overhead through
      header compression and more efficient connection management.
      While HTTP/2 and HTTP/3 support request multiplexing, EPP over
      HTTP requires commands to be processed sequentially, as described
      in Section 4.  Therefore, multiplexing does not enable concurrent
      execution of EPP commands.  Nevertheless, it can still provide
      performance benefits at the transport layer, such as reducing
      head-of-line blocking and improving overall connection efficiency.

   Latency:  The initial connection setup may incur additional latency
      due to TLS and HTTP negotiation phases.  Operators MAY encourage
      the use of persistent connections (e.g., HTTP Keep-Alive) to
      reduce the frequency of connection establishment.  However,
      persistent connections decrease the flexibility of a distributed
      architecture as outlined in Section 8.1.  On the client side, EPP
      sessions can be kept alive using the EPP <hello> command defined
      in [RFC5730], which can help reduce the need for repeated session
      establishment.

8.4.  Monitoring and Logging

   L7 Monitoring:  Operators can now monitor EPP traffic at the
      Application Layer (Layer 7).  Monitoring tools SHOULD track HTTP
      status codes (e.g., 200 (OK), 4xx, 5xx) in addition to EPP
      response codes to distinguish between transport-level issues and
      application-level errors.

   Logging:  In addition to EPP logs, HTTP access logs provide valuable
      metadata (e.g., source IP, request latency).  Operators MUST
      ensure that sensitive data (like EPP credentials in the login
      command or domain authinfo) is not leaked into HTTP logs as well
      as EPP logs.

8.5.  Security and Fault Management

   DDoS Mitigation:  The move to HTTPS allows for the use of modern DDoS
      protection services that are highly optimized for HTTP traffic.

   Fault Isolation:  When an error occurs, operators MUST be able to

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      identify if the fault lies at the TLS layer (e.g., expired
      certificate), HTTP layer (e.g., 413 Content Too Large), or EPP
      layer (e.g., 2200 Authentication error).

   Authentication:  HTTPS supports Client Certificate Authentication
      (mTLS).  As described in Section 9, the use of client certificates
      is RECOMMENDED to strengthen client authentication.  When mTLS is
      used, operational processes for credential rotation and revocation
      MUST be clearly defined and synchronized between the HTTP and EPP
      layers.

9.  Security Considerations

   Since client credentials are included in the EPP <login> command,
   HTTPS (Section 4.2.2 of [RFC9110]) MUST be used to protect them from
   disclosure while in transit.  HTTPS indicates that TLS is being used
   to secure the HTTP connection between the client and server.
   Transferring over TLS also prevents sniffing the HTTP session
   identifier and, consequently, impersonating a client to perform
   actions on registrars' objects.  Servers are REQUIRED to support TLS
   1.2 or higher and follow the Recommendations for Secure Use of
   Transport Layer Security (TLS) and Datagram Transport Layer Security
   (DTLS) [RFC9325] for the HTTPS connection.

   As a further measure to enforce the security, servers SHOULD require
   clients to present a digital certificate.  Clients who possess and
   present a valid X.509 digital certificate, issued by a recognized
   Certification Authority (CA), could be identified and authenticated
   by a server who trusts the corresponding CA.  This certificate-based
   mechanism is supported by HTTPS and can be used with EPP over HTTP.

   Servers are RECOMMENDED to implement additional measures to verify
   the client.  These measures include IP allow-listing and locking the
   HTTP session identifier to the client's IP address.

   HTTP session identifiers SHOULD be randomly generated to mitigate the
   risk of obtaining a valid one through a brute-force search.  HTTP
   session identifiers MUST be generated using a cryptographically
   secure random number generator and SHOULD contain at least 128 bits
   of entropy.  Servers MAY limit the lifetime of active sessions to
   avoid them being exchanged for a long time.

   The following server measures MAY also be taken:

   *  Restricting their scope through the Domain and Path attributes of
      the Set-Cookie header field to control cookie usage

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   The server MUST set the HttpOnly, Secure, and SameSite=Strict
   attributes on EoH session cookies.  The HttpOnly attribute prevents
   client-side scripts from accessing the cookie, the Secure attribute
   restricts transmission of the cookie to secure connections, and the
   SameSite=Strict attribute [I-D.ietf-httpbis-rfc6265bis] mitigates
   Cross-Site Request Forgery (CSRF) when these attributes are supported
   by the client.  Finally, servers are RECOMMENDED to perform
   additional checks to limit the rate of open EPP sessions and HTTP
   connections to mitigate the risk of congestion of requests.  Here
   again, IP allow-listing could also be implemented to prevent DDoS
   attacks.

   If the EPP server is configured as a load balancer routing the
   requests to a pool of backend servers, some of the aforementioned
   checks SHOULD be implemented on the load balancer side.

10.  Acknowledgements

   The authors wish to acknowledge the input from the .IT technical
   team.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC5730]  Hollenbeck, S., "Extensible Provisioning Protocol (EPP)",
              STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009,
              <https://www.rfc-editor.org/info/rfc5730>.

   [RFC6265]  Barth, A., "HTTP State Management Mechanism", RFC 6265,
              DOI 10.17487/RFC6265, April 2011,
              <https://www.rfc-editor.org/info/rfc6265>.

   [RFC7942]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status Section", BCP 205,
              RFC 7942, DOI 10.17487/RFC7942, July 2016,
              <https://www.rfc-editor.org/info/rfc7942>.

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   [RFC8095]  Fairhurst, G., Ed., Trammell, B., Ed., and M. Kuehlewind,
              Ed., "Services Provided by IETF Transport Protocols and
              Congestion Control Mechanisms", RFC 8095,
              DOI 10.17487/RFC8095, March 2017,
              <https://www.rfc-editor.org/info/rfc8095>.

   [RFC9110]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Semantics", STD 97, RFC 9110,
              DOI 10.17487/RFC9110, June 2022,
              <https://www.rfc-editor.org/info/rfc9110>.

   [RFC9112]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP/1.1", STD 99, RFC 9112, DOI 10.17487/RFC9112,
              June 2022, <https://www.rfc-editor.org/info/rfc9112>.

   [RFC9113]  Thomson, M., Ed. and C. Benfield, Ed., "HTTP/2", RFC 9113,
              DOI 10.17487/RFC9113, June 2022,
              <https://www.rfc-editor.org/info/rfc9113>.

   [RFC9114]  Bishop, M., Ed., "HTTP/3", RFC 9114, DOI 10.17487/RFC9114,
              June 2022, <https://www.rfc-editor.org/info/rfc9114>.

   [RFC9325]  Sheffer, Y., Saint-Andre, P., and T. Fossati,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
              2022, <https://www.rfc-editor.org/info/rfc9325>.

   [I-D.ietf-httpbis-rfc6265bis]
              Bingler, S., West, M., and J. Wilander, "Cookies: HTTP
              State Management Mechanism", Work in Progress, Internet-
              Draft, draft-ietf-httpbis-rfc6265bis-22, 1 December 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
              rfc6265bis-22>.

11.2.  Informative References

   [RFC7451]  Hollenbeck, S., "Extension Registry for the Extensible
              Provisioning Protocol", RFC 7451, DOI 10.17487/RFC7451,
              February 2015, <https://www.rfc-editor.org/info/rfc7451>.

   [I-D.ietf-opsawg-rfc5706bis]
              Claise, B., Clarke, J., Farrel, A., Barguil, S.,
              Pignataro, C., and R. Chen, "Guidelines for Considering
              Operations and Management in IETF Specifications", Work in
              Progress, Internet-Draft, draft-ietf-opsawg-rfc5706bis-06,
              12 August 2026, <https://datatracker.ietf.org/doc/html/
              draft-ietf-opsawg-rfc5706bis-06>.

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Appendix A.  Change History

A.1.  Change from 02 to 03

   1.  Added Dan Keathley and James Gould as co-authors.

A.2.  Change from 03 to 04

   1.  Clarified the difference between an EoH connection and an EPP
       session.
   2.  Added inclusion of the "Content-Type" header in every request and
       response except for the initial GET establishing the EoH
       connection.
   3.  Revised the Security Considerations section.

A.3.  Change from 04 to 05

   1.  Added the Implementation Status section with the Verisign EPP SDK
       implementation.
   2.  Removed the "Internationalization Considerations" section and
       added the EoH character encoding matching the EPP XML character
       encoding for the EPP Greeting, the EPP commands, and the EPP
       responses.
   3.  Added inclusion of the "Cache-Control" and "Expires" headers for
       the the EPP Greeting, the EPP commands, and the EPP responses.

A.4.  Change from regext 00 to regext 01

   1.  Added EPP Extension Registry registration for the EPP transport
       over HTTPS.

A.5.  Change from regext 01 to regext 02

   1.  Added IIT-CNR/Registro.it implementation.

A.6.  Change from regext 02 to regext 03

   1.  Added the "Operational Considerations" section.
   2.  Rearranged text of the "Security Considerations" section.
   3.  Minor edits.

A.7.  Change from regext 03 to regext 04

   Incorporated review feedback, including feedback from Mark
   Nottingham:

   1.   Replaced the "no-cache" directive with "no-store" in the Cache-
        Control header, and removed the Expires header.

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   2.   Replaced "HTTP return codes" with "HTTP status codes", "HTTP
        code 200" with "HTTP status code 200", and "HTTP codes" with
        "HTTP status codes".
   3.   Replaced the "pipelining" text in Message Exchange section with
        the recommended language.
   4.   Added a sentence related to the server defining the behavior
        when EPP pipelining is identified.
   5.   Clarified the relationship between the non-idempotent HTTP POST
        method and the idempotent application semantics of EPP commands.
        Conditioned client retries on transient failures, HTTP status-
        code semantics, and known idempotency of the complete EPP
        command, including any extensions.  Required a retry to contain
        the same EPP command and client transaction identifier, if
        present, and to preserve command ordering.
   6.   Changed "mapped onto a Hypertext Transfer Protocol (HTTP)
        session" to "mapped onto the Hypertext Transfer Protocol
        (HTTP)".
   7.   Required TLS 1.2 or later and deferred TLS configuration
        requirements to [RFC9325], removing the direct references to
        [RFC8446] and [RFC9155].
   8.   Added to introduction that this is a tunneling mapping.
   9.   Replaced the initial GET request with an empty POST request.
        Required a successful response to the initial POST request to
        use the 200 (OK) status code, contain the EPP Greeting, and
        establish the HTTP session; clarified that any other final HTTP
        status code means that no EoH connection was established.
   10.  Scoped the requirement to return an EPP response with 200 (OK)
        to requests that reach the EPP processing layer.  Clarified that
        an EoH server or intermediary can return other HTTP status codes
        for HTTP-layer failures.  Required clients to accept any HTTP
        status code, apply the class semantics of [RFC9110] to
        unrecognized codes, and treat the EPP command outcome as
        indeterminate when the command might have reached the EPP
        processing layer but no valid EPP response is received.
   11.  Added a Terminology section that defines a set of terms and
        their relationship, such as EoH, EPP connection / session, EoH
        connection /session, and HTTP session.
   12.  Distinguished instance-local state combined with session
        affinity ("sticky sessions") from an external shared session
        store, and described their implications for availability,
        failover, horizontal scaling, state protection, atomic updates,
        sequential processing, and session lifetime coordination.
   13.  Required the setting of the "Secure", "HttpOnly", and
        "SameSite=Strict" security attributes by the server in the
        Security Considerations and added the normative reference
        defining the SameSite attribute.

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   14.  Clarified that automatic retry of EPP POST requests is limited
        to EoH clients that understand EPP command semantics, and
        required operators to disable automatic retries in
        intermediaries under their control.
   15.  Added a set of message examples that include establishing the
        EoH connection via sending the initial POST with empty content
        and the EoH session via the EPP <login> command.
   16.  Clarified the Content-Type requirements for HTTP requests and
        responses carrying EPP messages and the Cache-Control
        requirements for HTTP responses.  Required a successful response
        to the initial POST request to include the X-Content-Type-
        Options header field with the value "nosniff", and required
        clients to fail the EoH connection if that response does not
        contain the expected EPP media type.
   17.  Added "There is no server discovery mechanism defined for EoH.
        The server URL for EoH is made available out-of-band by the
        server to the clients." to the Session Management section.
   18.  Changed the references to HTTP headers as header fields without
        the use of double quotes, per RFC 9110 conventions, and referred
        to Domain, Path, HttpOnly, and Secure as attributes instead of
        headers.
   19.  Addressed Status-code formatting.  Use 200 (OK), not "200 OK" or
        "HTTP code 200".  "413 Payload Too Large" -- the reason phrase
        is now "Content Too Large".  Use "content", not
        "payload"/"body".
   20.  Scoped the single-EPP-message requirement to EoH requests other
        than the initial empty POST request and the single-EPP-response
        requirement to responses generated after processing an EPP
        command.
   21.  Clarified the EPP connection and EPP session terminology and the
        client behavior when an HTTP response does not contain the
        expected EPP media type.
   22.  Required HTTP session identifiers to be generated using a
        cryptographically secure random number generator and recommended
        at least 128 bits of entropy.
   23.  Clarified that EoH uses the server URL provided out-of-band and
        uses port 443 as the default HTTPS port when the URL does not
        specify a port.
   24.  Made minor editorial corrections.

Authors' Addresses

   Mario Loffredo
   IIT-CNR/Registro.it
   Via Moruzzi, 1
   56124 Pisa
   Italy
   Email: mario.loffredo@iit.cnr.it

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   URI:   https://www.iit.cnr.it

   Lorenzo Luconi Trombacchi
   IIT-CNR/Registro.it
   Via Moruzzi, 1
   56124 Pisa
   Italy
   Email: lorenzo.luconi@iit.cnr.it
   URI:   https://www.iit.cnr.it

   Maurizio Martinelli
   IIT-CNR/Registro.it
   Via Moruzzi, 1
   56124 Pisa
   Italy
   Email: maurizio.martinelli@iit.cnr.it
   URI:   https://www.iit.cnr.it

   Daniel Keathley
   VeriSign, Inc.
   12061 Bluemont Way
   Reston, VA 20190
   United States of America
   Email: dkeathley@verisign.com
   URI:   http://www.verisigninc.com

   James Gould
   VeriSign, Inc.
   12061 Bluemont Way
   Reston, VA 20190
   United States of America
   Email: jgould@verisign.com
   URI:   http://www.verisigninc.com

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